Air compressor



Dec. 4, 1956 J BUSH AIR COMPRESSOR Filed 001;. 25, 1952 W-i-TIITI-a:

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United States Patent AIR COMPRESSOR J. Bush, Greensburg, Pa., assignorto Westingho'use Air Brake Company, Wilmerding, Pa., :1 corporation ofPennsylvania This invention relates to air compressors and moreparticularly to means for controlling the operating temperatureandoutput thereof. 1 v

In operation of certain air compressors of the multiple cylinder type,certain of the cylinders may be employed as air exhausting cylinders andcertain other cylinders as air compressing cylinders. The aircompressing cylinders draw air from the atmosphere and compress same fordischarge and use while the air exhausting cylinders withdraw air from:1 containing volume to be exhausted and discharge the withdrawn air tothe atmosphere with consequent waste thereof.

In view of the foregoing it 'is one object of the invention to providemeans whereby such otherwise wasted discharge of air from the airexhausting cylinders is employed to increase the output of compressedair from the' air compressing cylinders.

- In the operationof air compressors, excessive discharge temperatures,resultant from heat of compression, tend to damage or otherwise causefaulty operation of the discharge valve mechanism either as a directresult of such heat or as an indirect result of carbonized oil de-'posits, in viewof which, it is another object of the in vention toprovide a means and method whereby thetemperature of operation of an aircompressor maybe reduced from that otherwise obtaining.

"Other objects and advantages will become apparent from the followingdetailed description of the invention.

Inthe accompanying drawing, the single figure is a schematic view of amultiple cylinder air exhauster compressor device embodying a preferredform of the invention. 7 V

Description Referring to the drawing, the air exhauster-compressorapparatus embodying the invention comprises an air exhauster-compressordevice 1, a receiver 2, a pressure, relief valve device 3, and a storagereservoir 4. I

For sake of illustration, the air exhauster-compressor device 1 maycomprise three cylinders 5,6 and 7 mounted on a base or casing member 8common to each. Each 5 of the cylinders 5, 6 and 7 (referring inparticular to the cylinder 6 shown in cross-section in the drawing)comprises the usual hollow casing 9 having the usual piston 10reciprocable therein in sliding sealing engagement with the usual innercylinder wall 11 forr'nedin the casing. In the well-known manner, thepiston 10 serves as a movable abutment defining one end of the usualcylinder chamber 12, the opposite end of which chamber 12.,is closed bya pressure head 13 containing the usual inlet and discharge valves 14and 15, respectively, which control admission and release of fluid toand from the cylinder chamber 12, respectively; inlet valve 14 beingarranged for cooperation with a valve seat 17 to control communicationbetween an inlet port 18 in pressure head 13 and the cylinder chamber 12via an inlet chamber 16 constantly connected to port 18 and a bore 19 inwhich a fluted valve stem 19a attached to inlet valve 2 ,7 7 2,828Patented Dec. 4, 1 956 14 is slidably guided, and exhaust valve 15 beingdisposed in a discharge chamber 20 and arranged for cooperation with avalve seat 21 to control communication between discharge port 22 and thecylinder chamber 12 by way of the valve chamber 20 and a port 23. Alight compression spring 24 disposed in the inlet chamber 16 is arrangedto cooperate with the fluted stem 19a to bias the inlet valve 14 towardits seated position, in which it is shown in the drawing, closing ofithe cylinder chamber- 12 from the inlet port 18, and a similarcompression spring 25 disposed in the discharge chamber 20 is arrangedto-bias the discharge valve 15 toward its seated position, in which itis shown in the dr awing, closin'g off the cylinder chamber 12 from thedischarge port 22.1

In the well-known manner, movement of the respective piston 10 in eachof the cylinders 5, 6 and 7 through the suction stroke from top dead"center position in proximity of the pressure head 13 to bottom deadcenter position in which it is shown in the drawing in connection withcylinder 6, will cause a suction in cylinder chamber 12 which urgesunseating of inlet valve 14 and admission" of fluid into said chamber 12via inlet port 18, inlet chamber 16 and bore 19. Subsequent movementof'the piston 10 through-its compression stroke in the oppositedirection, i. e. from its bottom dead center position to its topdeadcenter position, will cause compression of the fluid in chamber 12 anddisplacement of such fluid therefrom via port 23, discharge-chamber 20and discharge port'22 by unseating of the respective discharge valve 15.a

'Each of the cylinders 5, 6 and 7 comprises the usual connecting rod 26which operablyf connects, via a pin 27, the respective piston 10 to theusual 'crankishaft" constantly open to 'the atmosphereby wayof' a portthrough the wall of casing 29.

A'partition 34, serving to. separate the chamber30 from the chamber 32,includes a central opening 35 extending therethrough from chamber tochamber for conveying fluid under pressure therebetween. A tapered valveseat encircling one end' of the central opening 35 in the partition 34serves to cooperate with a correspondingly tapered valve 36 dis posed inchamber 32 for controlling communication closing;olfi,communicationbetween the receiver 2, con

stantly'connected to chamber 30,; and the atmbsphere to p i whichchamber32 is constantly open. The valve 36 will be unseatedby'pressureoflfluid'in chamber30 u pon attainment of a, certain pressurevalue'sufficient to overi come the, opposing action of spring 37,whereupon coinmunication is established indevice'3 between chambersl 30and 32 via opening 35 to release fluid under pressure from the receiver2 to the atmosphere viapipe '31, and in device 3 the chamber 30,.opening 35, the unseated'f valve 3 6, chamber 32 and port 33 to limitthe degree of pressure of fluid in the receiver 2, against which the'exhauster cylinders 5 and 7 must operate, thus assuring thateffectiveness of said cylinders Sand 7 as exhausters will not beundesirably influenced by such back pressure 3 in receiver 2. Uponresultant reduction in pressure of fluid in the'receiver 2 to orbelow'the above mentioned 3 certain pressure value, the action of thespring 37 will seat the valve 36 to close the communication betweenchambers 30 and 32 via the opening 35 and prevent further release offluid under pressure from receiver 2 to the atmosphere via device 3 Thecylinder 6, for example, may be employed as an an compressing cylinderand as such is provided with a pipe 38 constantly connecting itsdischarge port 22 to the iiuid' pressure storage reservoir 4, while itsinlet port 18 is constantly open to the atmosphere.

The cylinders 5 and 7 maybe employed, for example, to exhaust" fluidunder pressurefrom a system via such" as'a'pipe 39- having branchesconnected ,to'the respective inlet ports 18 in said cylinders 5 and 7,to cause .fluid iromsaid pipe 39 to be drawn into the respective ,cylinder chambersn via the respective .ports 18, inlet. chambers-16andbores 19 by-unseating of the respective inlet valves 17 uponrepetitive movement of the respective pistons through: their suctionstrokes from top dead center to bottom dead center of piston travel.

According to a feature of the invention, the respective discharge ports22 in the cylinder devices 5 and 6 are connected via respective heatexchangers, such as finned pipes 40, to the receiver 2 forstorage offluid exhausted" from the pipe 39 and subsequent delivery of such fluid'to the air compressing cylinder 6 to increase output of compressedfluid from'same, rather than discharging such flu d to the atmosphere asis the usual practice. Thefluid under pressure supplied-by the.exhauster cylinders S and 7 to thereceiver 2' is admitted to thecompressor cyl nder 6, as through apipe 41 and a port 42 in casing 9 ofsaid cylinder. 6 opening radially into the respective cylinder chamber12. The port 42 opens into the cylinder wall ll ofcylinder -6in the pathof travel of piston 10 and s so located'with respect theretoas tobecovered by said: piston substantially during its suction andcompression strokes and tobe uncovered'duringfinal movement of;.the:,p1ston mcompleting its suction stroke and initial movement of thepiston inbeginning its compression 7 stroke; covering of the port 42 bypiston 10 closing off chamber 12 to the pipe41 while uncovering of saidport 42 by movement of piston 10 past same establishes fluid pressureconnection between said pipe 41 and said cham berl2,to allow foradmission; of .fiuid under pressure from the receiver 2 thereto; It willbe understood that;

during operation of-the compressor cylinder 6,.substan-' tially-a fullcharge of air,;from atmosphere is admitted 'underpressure to thecompressor cylinder'6 in'addition to its normal atmospheric charge willincreasethe-outputof said cylinder and result in-an-increase inefliciency of oper ation of the exhauste'r compressor device '1.

According to another'impo'rtant feature of the inven-' tron, the"flllld' ounder pressure discharged from the exhauster-cylinders -5 and 7ispreferably cooled subst'an tially to temperature of the atmosphere byassage" through-such as the finned pipes 40 err-route to'receiver'initial charge in said chamber 12. to avalue substantially equal to thatof the fluid in receiver 2, independently of compressive action ofpiston 10 and consequently at substantially constant temperature. Byvirtue of such initial pressurization of the compressor cylinder charge,the work required to be performed by the compressor cylinder 6 to raisethe initially pressurized charge to the desired discharge pressure isreduced below that which would be required were the initial charge atatmospheric pressure, with the result that the temperature of thecompressed fluid discharged from the. cylinder 6 isco'rrespondinglyreduced. The cooling effect of the receiver air admitted to thecompressor cylinder 6 enables same to be operated at a higher dischargepressure than would be practical otherwise due to the adverseefiect ofexcessive discharge temperature on operation of a compressor cylinder.

Having now described my invention, What Iclaim as new and desiretosecure by Letters Patent is:

I. In combination with a reservoir for storing compressed air, first,second, and third air compressing means, each of said compressing meansincludinga cylinder and piston, all said compressing means being ofsubstantially thesame capacity and .all said' pistons being connected tothe same prime mover for operation thereby, means connected to'saidfirst and second compressing means for cooling and storing the outputsthereof, said third conipressing means having an inlet and anoutlet,said outlet being connected to the reservoir, and means for admittingcooled air from said cooling andstoring means to said thirdcompressingmeans for addition to the air in said last namedcompressingmeans admitted through said inlet to increase the output ofcompressed air from the third compressing means and limit thetemperature rise therein resulting from heat of compression to a lowvalue, said first and secondcompressing means supplying air to saidco0l-, ingand storing means at avgreater rate than it is deliveredfrom-said coolingand storing means to said third compressing means tothereby insure that a substantial amount of cooledair at asubstantialpressure is always readily available for-introduction into said thirdcompressing meansl,

2. In combination with a reservoir for storing'compressed-air, firstandsecond air compressing means connected to a prime mover for operationthereby, means additionalto said first .air compressing means forcooling 7 to the cylinder chamber 12 before port 42 is uncovered 2-toremove its heat of compression prior to adrnissionbf; V

such fluid under-pressure to the compressor cylinder'6." The 'fluidunder pressure at atmospheric temperature th'us'- admitted intothecompressor-cylinder chamber 12 atthe endiof the inlet stroke of thecompressor cylinder piston 10 as-prjeviouslY described, willwiththe*charge"of*" during such inle t stroke and increase the pressureof the atmospheric air previousl'yjadmitted to said chamber 12andstoring the output thereof, conduit means connecting said first'air'compressing means to said cooling and storing means, valve meansinterposedin said conduit means for preventing air from escaping fromthe cooling and storing means back into thefirst air compressing means,said'second air compressing means having first and second inlets and anoutlet; saidoutlet being connected to the reservoir, and means connectedto said cooling and storing means and it! said second ,air compressmgmeans for V conducting cooled air' from said cooling and storing meansto said second air compressing means for admission there to through saidfirst'inlet and for addition to the airm said second air'compr'essingmeans admitted through said secondinlet'from a'source other than saidcoohn'g and 'st'ori-ngmeans, the capacity of said first air compressingmeans being substantially greater thanythe capacity of said second aircoinpres'sing means thereby providi'ng that air'is'supplied' to saidcooling and'storing means by'said first airj'compressingmeans at asubstantially greater rate' tha'n'it'jis' delivered from'said coolingandstoring means i .to said seco'n'dair'conip'ressing means and insuringthat air remains in sanction ng and storing means a substari tial periodof time and becomes effectively cooled, the 'adrnissionof theeftectively cooled air into said second air compressing means serving tolimit'to alow value the temperature rise in the'air therein'resultingfrom heat of 'cgmmession. v

3. Apparatus according to claim 2 including in addition meansoperatively connected to the cooling and storing 6 means for limitingthe pressure of the cooled air therein 1,182,372 Hippie May 9, 1916 toapreselected value. 1,264,562 Rix Apr. 30, 1918 1,445,073 Corpi Feb. 13,1923 References Cited in the file of this patent 1,467,489 NordbergSept. 11, 1923 UNIT 5 1,891,083 Dodge Dec. 13, 1932 866 457 G1,? STATESPATENT: t 17 1907 2,148,638 Patterson Feb. 28, 1939 1 s ep 899,720 ElderSept. 29, 1908 FOREIGN PATENTS 930,567 Shipley Aug. 10, 1909 314,498Germany Sept. 25, 1919

